1. Field of the Invention
This invention relates to method and apparatus for the diagnostic testing of engines, such as turboshaft engines, and, more particularly, to a motor/generator dynamometer system used to start an engine where mechanical energy produced by the engine is converted to electrical power for transmission to a local power grid for resale or consumption.
2. Description of the Prior Art
Engines operated by the armed forces generally utilize three levels of maintenance for their respective systems that include local level, intermediate level, and depot level. The support equipment determines the levels of maintenance that are provided. Generally, both intermediate and depot level maintenance require extensive load testing of all engines which are overhauled, repaired, and/or processed.
Conventionally turboshaft aircraft engines are tested on raised xe2x80x9cstandsxe2x80x9d or test xe2x80x9cplatformsxe2x80x9d. Engine breaking during the test is produced using the gearbox and propeller of an aircraft dedicated exclusively to the xe2x80x9cstand/test platformxe2x80x9d. This standard diagnostic test system allows an operator to complete the required test and evaluation which automatically produces a record for the engine""s log. These tests, particularly within a test cell create an adverse working environment due to the propeller producing a fine oil mist during the testing procedure. The operators spend much of their time working on the gear box and propellers. Currently, tests for engine performance use propellers for testing turboshaft aircraft engines.
A standard diagnostic test system is also used for testing turboshaft helicopter engines. Overall, the tests differ in the manner employed to load test the specific engines. In one application, the turboshaft helicopter engines are load tested with air dynamometers. Within a test cell an air dynamometer requires an air inlet and an outlet for the large volume of air used for the breaking action. Consequently, the test cell complexity is increased with the air inlet and exhaust outlet for both the turboshaft engine tested and the air dynamometer.
A known device for utilizing waste products to power a generator which provides electricity for a plant or for export is disclosed in U.S. Pat. No. 4,506,631. Municipal waste products are incinerated to release energy which is recovered to drive a steam or gas turbine. The turbine then drives a generator which changes the power into electricity. The electricity can be used by the plant or can be sold when demand is low.
U.S. Pat. Nos. 4,677,307; 4,394,582; and 4,715,192 disclose cogeneration systems which utilize exhaust heat to power turbines and electrical generators. The corresponding electricity can then be used to meet the changing demands of the facility or the very engine which powers the generator. U.S. Pat. No. 4,715,192 further discloses the ability to sell excess power to a local utility.
U.S. Pat. No. 4,752,697 discloses a cogeneration system which utilizes a heat engine to drive an electrical generator. The generator is coupled to the utility lines and provides supplemental power when necessary. In addition, supervisory means is provided for monitoring the electrical energy and/or power supplied by the generator, supplied by the utility, and consumed by the site.
U.S. Pat. No. 5,536,976 discloses a cogeneration system which adjusts to meet different heat and electrical demands of residential and small commercial sites. Excess power is sold to the utility upon generation. Means are provided for the synchronizing and paralleling necessary to operate the co-generator in parallel with the utility.
U.S. Pat. No. 4,338,788 discloses a cogeneration system in which a steam turbine of a power plant generator is directly linked to a stream of pressurized air from the fluidized catalytic cracking unit of a petroleum refinery.
U.S. Pat. No. 5,391,925 discloses a method for driving a large cooling system having a chiller compressor driven by a prime mover, such as a gas turbine. A reciprocating engine or a steam turbine in conjunction with an electric motor/generator is coaxially arranged on a common shaft. As the ambient temperature rises, the power demand of the compressor increases while the efficiency of the gas or steam turbine decreases. To compensate for the drop in power supply, additional driving power is supplied by the electric motor. Conversely, as the ambient temperature drops the compressor requires less power and the turbine""s efficiency increases. At this point, the turbine provides excess power to the compressor. The electric motor then operates as a generator and converts the excess power from the turbine into electricity which can then be used for internal use or can be sold to the local power grid.
The cost of commercial electrical utility usage is generally determined by a number of factors such as: (1) usage or consumption of electrical power, (2) load shedding by turning off electrical equipment during periods of peak demand for electrical power, and (3) peak shaving by producing on site electrical power during periods of peak demand. Generally, it is not economical for a utility to run large expensive, but efficient, power plants for short durations to meet peak demand. Peak demands are met by contract power, intercompany pool power, small generating plants such as hydroelectrical, turbo-generation, turbo-generation plus co-generation, diesel generation and the like. The smaller generating plants are not as efficient as the large generating plants, but they are quick to start and are far less expensive to capitalize.
Therefore, there is need for a motor/generator dynamometer system that provides diagnostic testing of turboshaft engines and serves as a source of electrical power supply. Once the engine is started, the motor/generator system would be switched to the generation of electrical power. The current and voltage of the generated electrical power would then be synchronized to that of a municipal or commercial power grid for consumption or resale.
A problem to be resolved in producing electrical power from turboshaft engine testing is scheduling the engine test during periods of peak demand to achieve peak shaving benefits. It would be unwise to subordinate an engine test program to attain the financial rewards for peak shaving as a utility function. On the other hand, with a sufficient engine test program, prudent management could easily attain the economics of peak shaving.
Producing electrical power from power shaft engine testing would serve to reduce the cost of electrical consumption and demand cost by load shedding. Savings would then be realized by increased manpower efficiency, reducing the activity/station local power company annual demand charge, generating credit or revenues by selling of electric current produced by the motor/generator dynamometer system, reducing maintenance and operating costs over old testing systems, and reducing the size of the test cell facility. In concert, these systems can provide emergency generation immediately for local or grid requirements.
In accordance with the present invention there is provided a method for supplying electricity to an electrical power system that includes the steps of starting an engine under test. Mechanical energy is generated from a test conducted on the engine. The mechanical energy produced by the engine under test is transferred through a power transfer mechanism to a generator. The mechanical energy is converted into electricity by the generator. The electricity produced by the generator is measured to obtain a load for establishing the power of the engine being tested. The electricity produced during testing of the engine is supplied to an electrical power system for consumption.
Further, in accordance with the present invention there is provided apparatus for converting mechanical energy produced during testing of an engine to electricity that includes an engine under test. A generator is coupled to the engine. A mechanism is provided for transferring the mechanical energy produced by the engine during testing to the generator for conversion to electricity. The electricity produced by the generator is measured to obtain a load for evaluating the power produced by the engine under test. A power conditioner connects the generator to an electrical power system to adjust the electricity produced by the generator during testing of the engine for supply to the electrical power system.
In addition, the present invention is directed to a method for converting mechanical energy produced during the testing of an engine to electricity for power consumption that includes the steps of starting an engine under test. Mechanical energy and exhaust are generated from testing the engine. The mechanical energy generated from testing the engine is transferred to a generator. The mechanical energy is converted by the generator to electricity. The electricity produced by the generator is conditioned for transmission to an electrical system for power consumption. The engine exhaust is fed to a steam boiler for generation of steam. The steam produced by the steam boiler is fed to a steam turbine. Mechanical energy is generated from the steam fed to the steam turbine. The mechanical energy produced by the steam turbine is transferred to a generator. The mechanical energy is converted by the generator to electricity. The electricity produced by generator is conditioned for consumption by an electrical power system. The conditioned electricity generated from testing the engine is supplied to the electrical power system.
Accordingly, a principal object of the present invention is to provide a motor/generator system for testing engines where the mechanical energy generated from the engine test is converted at a test stand by a motor/generator to electricity which is conditioned for transmission to an electrical power system for consumption.
Another object of the present invention is to provide a method for transferring electrical power generated during the testing and maintenance of a turboshaft engine to an electrical power grid to reduce the cost of electrical consumption.
A further object of the present invention is to provide method and apparatus for testing the performance of turboshaft engines, such as aircraft engines, in the maintenance and repair of the engines and convert the energy generated from the engine testing to electrical power to supplement the electrical power supplied by an electrical utility company during periods of peak power demand.
An additional object of the present invention is to provide a turboshaft engine testing system that utilizes a generator for converting mechanical energy produced by an engine under test to electrical power which is supplied to a local power grid for resale and/or consumption where the generator is also operable as a motor to start the engine under test and a dynamometer for measuring the mechanical energy generated by the engine during testing.
Another object of the present invention is to provide apparatus for testing the performance of an engine by converting the mechanical energy generated by a turboshaft of the engine to electrical power for transmission to a power grid of a municipal power supply for usage during periods of peak power demand to achieve peak shaving benefits to the power supply system and when necessary provide emergency power xe2x80x9con sitexe2x80x9d or to the grid.